Interior Permanent Magnet (IPM) machines generally include a rotor having a plurality of magnets of alternating polarity around an outer periphery of the rotor. The rotor is rotatable within a stator which generally includes a plurality of windings and magnetic poles of alternating polarity.
An IPM machine may use either ferrite magnets or rare earth magnets, such as NdFeB. Ferrite magnets are less expensive, but produce a lower performance compared to rare earth magnets when utilized in identically configured IPM machines. In order to increase the performance of IPM machines using ferrite magnets, the ferrite magnets must be buried deep inside the rotor core, near a center of the rotor, such that a large amount of magnetic material may be packed in the rotor. However, when utilizing conventional arc magnet geometry, in which a radial center of arcuate shaped magnets within a pole of the rotor are arranged concentric with each other, the number of poles of the internal permanent magnet machines must be reduced to accommodate a larger circumferential length of each pole. Additionally, radially outer layers of magnets within a pole of the rotor are small with a sharp radius, which are difficult and expensive to produce and assemble.